Matrix Data Results Explanation

I have three 5x5 matrices attached here, Lat, Lon, and Data:

I am using the following code:

Lat = [-1 -1 -1 -1 -1;
-2 -2 -2 -2 -2;
-3 -3 -3 -3 -3;
-4 -4 -4 -4 -4;
-5 -5 -5 -5 -5];

Lon = [-50 -40 -30 -20 -10;
-50 -40 -30 -20 -10;
-50 -40 -30 -20 -10;
-50 -40 -30 -20 -10;
-50 -40 -30 -20 -10];

Data = [1 2 3 4 5;
6 7 8 9 10;
11 12 13 14 15;
16 17 18 19 20;
21 22 23 24 25];

intervaloLat = [-3.5, -1.5];
intervaloLon = [-35, -15];

latDentroDoIntervalo = Lat >= intervaloLat(1) & Lat <= intervaloLat(2);

lonDentroDoIntervalo = Lon >= intervaloLon(1) & Lon <= intervaloLon(2);

Resultado = Dados(latDentroDoIntervalo(:,1) & lonDentroDoIntervalo(1,:));

The result of Data should be 2x2: [8, 9; 13, 14]

And it should not be: [8; 13; 9; 14]

Answer 1

[Fangjun Jiang]

The code looks good and shows good programming flow to use logical index. It will be very lengthy to explain why the result shows in that way. Maybe, if you replace your last line of code with the three lines below, the result would make more sense to you.

You can check the value of every variable after every step to make sense of the size and value of the variable.

Lat = [-1 -1 -1 -1 -1;
    -2 -2 -2 -2 -2;
    -3 -3 -3 -3 -3;
    -4 -4 -4 -4 -4;
    -5 -5 -5 -5 -5];

Lon = [-50 -40 -30 -20 -10;
    -50 -40 -30 -20 -10;
    -50 -40 -30 -20 -10;
    -50 -40 -30 -20 -10;
    -50 -40 -30 -20 -10];

Data = [1 2 3 4 5;
    6 7 8 9 10;
    11 12 13 14 15;
    16 17 18 19 20;
    21 22 23 24 25];

intervaloLat = [-3.5, -1.5];
intervaloLon = [-35, -15];

latDentroDoIntervalo = Lat >= intervaloLat(1) & Lat <= intervaloLat(2)

latDentroDoIntervalo = 5×5 logical array
   0   0   0   0   0
   1   1   1   1   1
   1   1   1   1   1
   0   0   0   0   0
   0   0   0   0   0

lonDentroDoIntervalo = Lon >= intervaloLon(1) & Lon <= intervaloLon(2)

lonDentroDoIntervalo = 5×5 logical array
   0   0   1   1   0
   0   0   1   1   0
   0   0   1   1   0
   0   0   1   1   0
   0   0   1   1   0

index=latDentroDoIntervalo & lonDentroDoIntervalo

index = 5×5 logical array
   0   0   0   0   0
   0   0   1   1   0
   0   0   1   1   0
   0   0   0   0   0
   0   0   0   0   0

Resultado = zeros(size(Data))

Resultado = 5×5

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

Resultado(index)=Data(index)

Resultado = 5×5

0 0 0 0 0 0 0 8 9 0 0 0 13 14 0 0 0 0 0 0 0 0 0 0 0

Or, you can do it this way. This only applies when your "selected area" is "square".

RowIndex=find(all(latDentroDoIntervalo,2))

RowIndex = 2×1

2 3

ColIndex=find(all(lonDentroDoIntervalo,1))

ColIndex = 1×2

3 4

Resultado=Data(RowIndex,ColIndex)

Resultado = 2×2

8 9 13 14

[Augusto Gabriel da Costa Pereira]

Veeeeeeeeeery good your code. Thaks!!!